The present invention relates to processing of video images and, in particular, it concerns systems and methods for producing personalized video clips in which a subject appears together with elements of a pre-recorded video clip.
It is known to mix video images by various techniques. One of the most common techniques for achieving a high quality superposition of a subject over a pre-existing image is chroma-key.
The chroma-key technique involves filming a subject in front of a monochrome background, typically blue, under uniform shadowless lighting conditions. This ensures that all parts of the image other than the subject himself have a constant precisely defined color and brightness. The blue pixels are then "keyed-out", i.e., regarded as transparent, during superposition over a pre-existing image during mixing. The result is that the subject appears seamlessly as a part of the pre-existing clip.
For convenience of reference, the keyed image is referred to as the "foreground image" since it is superimposed over the second image during mixing. Conversely, the full-frame non-keyed image is termed the "background image" since a part of it is obscured during the mixing process.
Chroma-key techniques have been used extensively in film and television studios for such applications as news presentation and comic effects. Where the subject is required to appear to interact with some element of the background image, a real-time display of the mixed image is provided as visual feedback to the subject.
The very specific filming conditions required for the foreground image make the technique very expensive. As a result, high quality chroma-key type combined video sequences have hitherto only been available to production teams working in the context of a professional movie studio.
There is therefore a need for low cost systems and methods which would employ keyed-superposition techniques to generate high quality personalized combined video clips of a subject together with graphic elements of interest under normal lighting conditions. It would also be advantageous to have systems which provide additional visual indications which appear to verify the simultaneous presence of the subject and the graphic elements of interest within a video clip.